First Map of an Alien World

This is the first-ever map of the surface of an exoplanet, or a
planet beyond our solar system. The map, which shows temperature
variations across the cloudy tops of a gas giant called HD 189733b, is
made from infrared data taken by NASA's Spitzer Space Telescope. Hotter
temperatures are represented in brighter colors.

HD 189733b is
what is known as a hot-Jupiter planet. These sizzling, gas planets
practically hug their stars, orbiting at distances that are much closer
than Mercury is to our sun. They whip around their stars quickly; for
example, HD 189733b completes one orbit in just 2.2 days. Hot Jupiters
are also thought to be tidally locked to their stars, just as our moon
is to Earth. This means that one side of a hot Jupiter always faces its
star.

As predicted, the map reveals that HD 189733b has a warm
spot on its "sunlit" side, which is always pointed toward the star. But
the map also shows that this spot is offset from the high-noon, or
sun-facing, point by 30 degrees. According to scientists, ferocious
winds traveling up to 6,000 miles per hour (nearly 9,700 kilometers per
hour) are probably pushing the hot spot to the east.

In addition
to the warm spot, the map tells astronomers that temperatures on HD
189733b are fairly even all around. While the dark side is about 1,200
degrees Fahrenheit (650 degrees Celsius), the sunlit side is just a bit
hotter at 1,700 degrees Fahrenheit (930 degrees Celsius). This mild
temperature variation is more evidence for strong winds, since winds
would help spread the heat from the hot, sunlit side over to the dark
side.

These data were collected by Spitzer's infrared array
camera as the planet, a so-called transiting planet, passed in front of
its star, then swung around and disappeared behind it (see animation).
By observing the planet for half of its 2.2-day long orbit, Spitzer was
able to measure the infrared light, or heat, coming from its entire
surface.

The Spitzer Space Telescope is a NASA mission managed by the Jet Propulsion Laboratory. This website is maintained by the Spitzer Science Center, located at IPAC on the campus of the California Institute of Technology.